Regenerative heat exchanger



y 1965 w. c. BUBNIAK ETAL 3,181,603

REGENERATIVE HEAT EXCHANGER Filed Dec. 4, 1961 2 Sheets-Sheet l .murk

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ATTORNEY y 1965 w. c. BUBNIAK ETAL 3,181,603

2 Sheets-Sheet 2 Filed Dec. 4, 1961 .4 (95/271952 Az/JM United States Patent Ofilice 3,181,603 Patented May 4, 1965 3,181,603 REGENERATIVE HEAT EXCHANGER William C. Bubniak, Warren, Robert J. Motfat, Oak Park,

and James R. Mondt, Warren, Mich, assignors to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed Dec. 4, 1961, Ser. No. 156,599 8 Claims. (Cl. 165-9) This invention relates to rotary regenerative heat exchangers and more particularly to the sealing problems associated therewith.

Regenerative heat exchangers commonly employ a drum or disc shaped matrix which rotates Within a hous ing that provides separate chambers to direct hot and cold fluids through the matrix. Heat picked up from the hot fluid in one chamber is transferred to the cold fluid in the other chamber as the matrix rotates. The matrix rotates through closely fitting seal passages between the chambers, and in order to reduce leakage across the seal passages, it is necessary that the hot and cold sides of the matrix maintain a close fit with the walls of the passages, and it is also necessary that the matrix heat exchange elements be so arranged that fluid flow through the matrix cannot occur laterally of the hot and cold sides. Minimum leakage is not accomplished in conventional regenerators because the temperature gradient across the matrix thermally distorts it so that it does not conform to the shape of the seal passages. When the clearances between the passages and the hot and cold sides of the matrix are made large enough to prevent interference, appreciable leakage between the chambers results.

An object of the invention is to provide a matrix for rotary regenerators in which thermal distortion of the matrix sealing elements is minimized so that the sealing clearances and leakages are likewise minimized. How this and other objectives are accomplished will be apparent from the following description and accompanying drawings showing a preferred form of the invention.

In the drawings:

FIGURE 1 is a schematic view of a rotary regenerative heat exchanger incorporating the invention;

FIGURE 2 is a side view, partially broken away, of a portion of the drum matrix of FIGURE 1;

FIGURE 3 is a sectional view taken in the direction indicated by the line 3-3 of FIGURE 2 and partially broken away to illustrate various elements of the matrix; and

FIGURES 4, 5 and 6 are perspective views of various heat exchange elements which may be employed in the matrix.

Referring to FIGURE 1, a housing 10 has a wall 12 forming heat transfer chambers 14 and 16 and a drum matrix 18 of stainless steel rotatably driven therein which passes through seals 20 and 22 that incorporate rectangular passages 24 that fit closely about the rim of the matrix 18 to prevent fluid leakage between the chambers. This type of regenerator is well known and it is not believed necessary to show known details and features which are not material to the present invention. Reference may be had, if desired, to U.S. Patent No. 3,057,604 for Rotary Regenerator, of Bubniak et al., issued October 9, 1962, for other details.

The regenerator can be used with a gas turbine whereby air from the compressor enters the chamber 14 at the inlet side 26, passes through the matrix 18 as indicated by the arrow A, is heated thereby and exhausts from the chamber 14 on the outlet side 28. The air is then fed to a combustion chamber and expanded through a turbine whereupon the turbine exhaust is fed to the inlet side of the chamber 16 and passes through the matrix 18 in the direction indicated by the arrow B to the discharge side 32 of the chamber 16. In an arrangement such as this, the drum runs with a hot inner side, as noted, and with a decreasing temperature to the cold outer side which results in nonconformity between the heat exchange elements and the seal.

Referring to the remaining figures, the drum 18 is fashioned from a structural framework that includes a pair of end rings 34 and 36 rigidly interconnected by axially extending bars 38 held in tongue and groove connections 40 and 42 by keys 44. Gear teeth 46 may be formed on the end rings to provide a rotary drive means for the drum. The matrix frame comprising the end rings 34 and 36 and the cross bars 38 provide support for a plurality of heat transfer lamellations 48 which direct the fluid flow through the matrix and which serve as the primary heat transfer material. The matrix framework is of suflicient thickness to have enough heat conductivity to maintain a moderate temperature gradient and thus avoid undue thermal distortion. The heat transfer lamellations, on the other hand, are composed of a stack of many thin strips or lamellae for maximum heat transfer effectiveness and are thus subject to an extreme temperature gradient which cause thermal distortion.

Each lamellation consists of labyrinth sealing lamellae 50 and non-sealing lamellae 52 which are stacked together in alternating relation. The sealing lamellae 50 each comprises a pair of fiat strips 54 and 56 which are spot welded to each other along their cold edge 56 and to a substantially isothermal sealing beam 60 which is also located at the cold edge. The ends of the lamellae 5t) dovetail into the end rings 34 and 36 for radial retention. The thin strips 54 and 56 extend unconnected to each other from the beam 60 to their hot edges 62 and are provided with lengthwise extending, staggered slots 64 and 66 that extend from the hot edges 62 to the isothermal beam 60.

Referring to FIGURES 1 and 2, it will be noted that the sealing lamellae 50 extend radially inward and outward of the non-sealing lamellae 52 and structural ribs 38. The sealing lamellae 50 fit very closely in the rectangular passages 24 provided by the seals 20 and 22 and they are relied upon to prevent leakage between the chambers 14 and 16. The passage 24 contains a number of sealing lamellae 50 at all times and thus provides a labyrinth seal against the large pressure differential existent between the chambers 14 and 16.

It is well known that a strip of metal heated along one edge and cooled along the opposite edge will warp or bow in the direction of the heated edge. A familiar example of this phenomenon is the tendency of a thin frying pan to oilcan toward the burner when first placed thereon. Because of this action, the radial ribs 38 bow slightly in the direction of the drum interior during regeneration operation. This distortion is not too pronounced as the ribs are relatively thick and thus have suflicient conductivity to avoid a large temperature gradient. Also, the slight bowing of the ribs 38 is of no consequence to the sealing arrangement as they do not extend far enough radially to determine the sealing area, and this is likewise true of the nonsealing lamellae 52.

In spite of the above discussed phenomenon, the sealing lamella 50 will retain a substantially rectangular shape in the passage 24 even though a severe temperature gradient exists across it. Referring to FIGURES 2 to 4, it is seen that the isothermal sealing beam 60 is considerably thicker than the strips 54 and 56 and that the beam is much narrower than these strips. There is accordingly no effective temperature gradient in the isothermal beam 60 as compared to the fluid whereby the beam can maintain a substantially straight line clearance relation with the walls of the passage 24. The strips 54 and 56 do have a high temperature gradient from their hot edges 62 to their cold edges 58 and there would thus be a tendency for these strips to bow convexly toward the hot side. This bowing tendency is overcome along the cold edge' 58 by the attachment of the strips to the structurally stronger isothermal beam 60 and is minimized on the hot edge 62 by the slots 64 and 66 The many slots in each of-the strips divide? each into many sections and, instead of the bowing occurring from one end of the strip to'the other, as in a nonslotted strip, it now occurs only between the ends of the sections and is reduced proportionately in radial dieach other, by wall structure and a rotary matrix in the chambers having hot and cold sides passing laterally through a closely fitting labyrinth sealing passage in the rection. The'slots 64 are staggered with respect to the slots 66 in order that fiuid transfer may not take place through the matrix in a circumferential direction.

The non-sealing lamellae 52 maybe of anysuitable configuration. FIGURE shows'a typical form and comprises a thin corrugated sheet 68 to which is secured, as by spot welding, a plurality of flat plates 70 with the corrugation providing the usual multitude of radially directed heat transfer fluid flow paths. .The non-sealing lamellae 52 have tongue and groove connections with the end rings 34and 36 in the same manner as the sealing lamellae 50 and several lamellae 52 are stacked together between each of the spaced lamellae 50.

In FIGURE 6 is seen another sealing .lamella which may be used in practicing the invention in place of 'the sealing lamella 50.- The alternate sealing lamella 72 comprises a substantially isothermal beam 74 at the cold edge 76 and a corrugated strip 78 spot welded thereto and extending from the beam to the hot edge 80. this instance, the tendency of thecstrip 78 tobow conwall structure, the matrix having a structural framework formed 'by spaced rib interconnected rings and hav'- 1 ing heat transfer lamellations formed by lamellae stacked between the rings to provide fluid transfer across the hot lamellae and isothermal sealing beams thick and narrow vexly: toward the hot side of the temperature gradient is overcome by; the structural opposition of the isothermal beam, 74 which 'is able to accomplish this because of the weakening effect lengthwise, ofthe corrugations on the strip 78. In other words, the beam 74 maintains the col-d edge of the strip 78 in alignment because it is stronger andfastened. there and the corrugation insures that the hot edge 80 is likewise kept in alignment because it is stronger *in a radial'direction from the beam than it is lengthwise. v a

While the preferred embodiment ofthe invention has been shown in detail, it is apparent that otherembodiments within the scope of the invention may be made by the exercise of ordinary'skill in; the art. For example, it is notnecessary that the isothermal'beams 60 be located only at the outer periphery of the drum matrix 18 for they can be located on the inner periphery'by merely inverting the lamellae 50. Moreover, the lamellae can be '50 arranged as to have their isothermal beams alternating between the inner and outer periphery. -The beams are preferably located on theouter periphery, howievcr, in order to provide the greatest possible mass of heat exchange material in agiven drum diameter. The invention can likewise be applied to rotary regenerators employing a disc matrix and, in this instance, the ribs 38 would extend radially from inner and outer diameter end rings with the lamellae 50 and 52 extending radially of the disc.

We claim: 7 1. In a regenerative heat exchanger of the type having a housing forming heat transfer chambers separated from relative the lamellae and rigidly secured respectively along labyrinth sealing lamellae comprise strips secured to the isothermal sealing beam, the strips being slotted fromthc beam to the other edge.

- 6. The improvement set forth in claim 2 wherein a labyrinth sealing lamella comprises a pair of overlapped strips secured together at the isothermal sealing beam, the strips being slotted in staggered relation from'the beam to the inner. periphery of the matrix.

7. The improvement set. forthin claim. 1 wherein a labyrinth sealing'lamella' comprises a corrugated strip secured to the isothermal sealing beam with the corrugations running transverse the length of the beam. 8. The improvement set forth in claim 2 wherein a labyrinthsealing lamella comprises a corrugated strip secured to the 'isothermal'sealing'beam with the corrugations running in radial direction.

References Cited by the Examiner UNITED STATES PATENT CHARLES SUKALO, Primary Examiner. ALDEN D. STEWART,Examine.r. 

1. IN A REGENERATIVE HEAT EXCHANGER OF THE TYPE HAVING A HOUSING FORMING HEAT TRANSFER CHAMBERS SEPARATED FROM EACH OTHER BY WALL STRUCTURE AND A ROTARY MATRIX IN THE CHAMBERS HAVING HOT AND COLD SIDES PASSING LATERALLY THROUGH A CLOSELY FITTING LABYRINTH SEALING PASSAGE IN THE WALL STRUCTURE, THE MATRIX HAVING A STRUCTURAL FRAMEWORK FORMED BY SPACED RIB INTERCONNECTED RINGS AND HAVING HEAT TRANSFER LAMELLATIONS FORMED BY LAMELLAE STACKED BETWEEN THE RINGS TO PROVIDE FLUID TRANSFER ACROSS THE HOT AND COLD SIDES AND TO PREVENT FLUID TRANSFER LATERALLY OF THE SIDES, THE IMPROVEMENT COMPRISING LABYRINTH SEALING LAMELLAE ALTERNATED IN EACH LAMELLATION WITH HOT AND COLD EDGES CLOSELY FITTING IN THE LABYRINTH SEALING PASSAGE AND EXTENDING BEYOND THE HOT AND COLD EDGES OF THE REMAINING LAMELLAE AND ISOTHERMAL SEALING BEAMS THICK AND NARROW RELATIVE THE LAMELLAE AND RIGIDLY SECURED RESPECTIVELY ALONG ON EDGE ONLY OF EACH OF THE LABYRINTH SEALING LAMELLAE. 